Hey Nick @wproyal,
In the Pro version of our plugin we have a ‘permanent’ setting to never update the feed at all, and there shouldn’t be any max in the time to update the cache. Should you run into any issues with your current interval or the images show and issues going forward please send us a support request on our site here, sending us your System Info. When you had issues last time, is it possible this happened since October 24th? There was an API change then that caused a change that we had to push out an update for, specifically breaking all of our users’ feeds. After an update, the cache would also need to be cleared to ensure the images were retrieved using the new way.
I would also in your case go to Instagram Feed > Customize and ensure ‘Favor Local Images‘ is enabled so that they are served from your server and not the Instagram API.
Best regards,